The term 100th Anniversary can be expressed in three different ways: Centennial (10 letters), Centenary (9 letters), and Firstcentennial (15 letters). Centennial is derived from the Latin word centum, meaning one hundred. Centenary is a combination of the Latin words centum and annus, meaning one hundred years. Firstcentennial is a combination of the Latin words primus, meaning first, and centum, meaning one hundred. All three terms refer to the same event, which is the celebration of a hundredth anniversary.